Method and apparatus for pumping blood within a vessel

ABSTRACT

A dynamically augmenting pump system incorporates a sealed liquid-filled catheter which is inserted into a vessel such as an artery, and the pump system is operated in timed relation with the heart to aid the heart during episodes of impairment or failure of cardiac function by producing higher frequency pulsation or pressure waves within the blood during diastole and during the isometric contraction period of the heart. This frequency of pulsation is adjusted to the dynamic transmission characteristics of a selected circulatory subsystem, such as the coronary vascular system, to assure the transmission of a maximum of pulsatile energy into the subsystem. The catheter provides energy to maintain adequate blood flow through the healthy part of the myocardium and has a passage for injecting successive quantities of medication into the coronary arteries. The pump system also functions to penetrate the ischemic myocardial tissue with arterial blood and medication. The pump system may also be used to provide enhanced perfusion for other parts of the systemic circulatory system, for example, to prevent such detrimental effects as renal failure. Any one or combination of the functions may be used depending on the special medical conditions of the patient.

RELATED APPLICATION

This application is a continuation of application Ser. No. 841,017,filed Oct. 11, 1977 which issued on May 15, 1979 as U.S. Pat. No.4,154,227.

SUMMARY OF THE INVENTION

In one embodiment, a sealed liquid-filled catheter has a hydraulicallyinflatable bulbous tip and is inserted into a proper artery of a patientso that the tip is advanced close to the aortic valve. The catheter alsohas a small open ended passage which facilitates the injection ofmedication or radiopaque solutions for angiographic purposes, and alsotransmits aortic pressure to an extra-corporeal transducer for pressurerecording. The primary liquid-filled catheter passage functions as aconduit to inject and withdraw the liquid from the inflatable tip sothat the tip expands and collapses at a controlled higher frequency andin timed relation with the heart pulse.

The inflation of the catheter tip generates pressure waves in the aorta,and an oscilloscope displays the aortic pressure and a superimposedtrain of pressure waves. These waves travel in the proximal and distaldirections thus transmitting energy in both directions. The energytransmitted towards the coronary arteries is greater than thattransmitted distally. The resulting pressure amplitudes in the coronaryarteries can be a multiple seven to ten times the natural pressure waveamplitude in the aorta if the frequency of tip inflation and deflationis properly adjusted to the transmission characteristics of the aortaand coronary arteries.

Other features and advantages of the invention will be apparent from thefollowing description, the accompanying drawings and the appendedclaims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an augmenting pump and medication pump systemconstructed in accordance with the invention and showing the catheter inenlarged axial section with the tip portion inflated;

FIG. 2 is an enlarged axial section of the catheter tip portion whendeflated;

FIG. 3 illustrates the inflated and deflated catheter tip portion in theaorta adjacent the heart valves;

FIG. 4 is a typical display on a multi-channel oscilloscope connected tomonitor the aortic pressure, the ECG R-wave, and the volume of injectedmedication;

FIG. 5 is a schematic block diagram of an electronic control system foroperating the augmenting pump shown in FIG. 1; and

FIG. 6 is another schematic block diagram of an electronic controlsystem for operating both the augmenting pump and medication pump shownin FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 1, a flexible catheter 10 is constructed of anon-resilient flexible material and includes a tip portion 12 which isinflatable between a collapsed condition (FIG. 2) and a generallyspherical inflated condition with a center indentation (FIG. 1) when thetip portion has a volume of approximately three cubic centimeters. Thetip portion 12 is inflated and deflated at a selected frequency by meansof pumping and withdrawing a hydraulic fluid or liquid such as a salinesolution through a primary passage 14 defined by a tubular portion 16.The catheter 10 also defines a smaller passage 17 which is defined by anintegrally molded tubular portion 18 having a tip or end portion 19which projects axially or forwardly from the inflatable tip portion 12of the catheter. As illustrated in FIG. 3, the catheter 10 is insertedinto a patient's artery so that the inflatable tip portion 12 is locatedwithin the aorta 25 close to the aortic valve 26. The pressure wavesproduced by inflating and deflating the tip portion 12 are effective totransmit the primary energy towards the coronary arteries 27 and 28.

The changes in position of the inflatable catheter tip portion 12 and/orthe changes of the frequency of tip inflation and deflation providecontrol over the relative amounts of energy transmitted both forwardlyand rearwardly. This permits vascular sections, either proximal ordistal to the tip location, to be selected as the major recipients ofpulsatile energy. The pulsatile energy substitutes for all or a part ofthe cardiac work reduction which occurs in cases of cardiacinsufficiency. The beneficial effect of this energy in most cases ofapplication is the intermittent elevation of blood pressure and flowmomentum to normal levels in order to maintain some minimum penetrationof high resistant vascular beds and tissue, thus minimizing thepossibility of permanent organ or tissue damage.

The tissue of primary interest is the myocardium. Beneficial effects areprovided for the intact part of the myocardium and the ischemic hypoxicpart. The intact part of the myocardium will receive an adequate amountof blood through either alternating or stepwise increasing pressure andflow pulses during the diastolic period. The frequency of the pulses isadjusted according to the location of the tip portion 12 in relation tothe coronary ostiae and the known transmission characteristics of theintermediate section of aorta and the coronary arteries in order tofacilitate an optimum transmission of energy into the myocardium. A 20Hz component is desirable, for example, if the tip portion 12 is placedclose to the coronary ostiae.

Critical closing pressures at several levels are known in themyocardium. The highest levels of these critical closing pressures areexceeded by the pump system of the invention to produce a completepenetration of the healthy part of the myocardium. This is of particularimportance for the subendocardial layers which offer the greatestresistance to flow and are most prone to damage in ischemia.

The subepicardial vasculature is completely closed during the systolicperiod through the squeezing effect of the contracted myocardial muscle.The epicardial vessels are patent because they are located in theepicardial surface rather than embedded in the myocardium. These vesselscan receive blood during the systolic period but they cannot pass it on.Pressure and flow pulses inside the surface vessels are thereforereflected back and the superposition of incident and reflected wavesproduces high pressure values.

Collapsed collateral vessels exist normally between the major coronaryarteries of the human heart, and are most numerous around the apex. Thevessels are also known to be patent in some healthy humans,approximately 100 hours after an infarction, and occasionally aftertreatment with certain pharmaca prior to an infarct. The effect ofgenerated elevated pressure pulses in accordance with the invention isthe accelerated recruitment of collateral connections and the subsequentsalvation of a greater mass of infarcted tissue than during the naturaldevelopment of collateral connections.

The above treatment is aided by the injection of drugs through themedication catheter tube 18 and its projecting tip or end portion 19.The effects of these drugs are twofold. The amount of fluid passingthrough the initially opened collateral vessels is very small incomparison to the normal influx of blood into that area and may not besufficient to avoid myocardial damage. The initially entering fluid,therefore, carries pharmaca which arrest the biochemical breakdown inthe ischemic area before it becomes irreversible. Additionalpharmacological agents may be applied to accelerate collateraldevelopment, in particular lumen increase, and assure an adequate supplyof blood for the infarcted area at the earliest possible time.

The treatment of the ischemic myocardium requires the tip portion 12 tobe inflated during the systolic period. However, the inflation must belimited to the isometric contraction period of the myocardium. Thesubepicardial vessels are already closed but the ventricle does noteject blood into the aorta 25. When this ejection occurs, the tipportion 12 is collapsed in order to decrease the ventricular afterload.This requirement and the necessary speed of operation due to the tiplocation and optimal tuning to cardiovascular dynamics requires adynamically acting relatively small tip portion 12. The extracorporealequipment for the control and timing of the tip portion performance istuned to the dimensions and dynamics of the catheter 10 including thetip portion.

The augmentation pump system of the invention includes two major partswhich are the electro-mechanical assembly shown in FIG. 1 and itselectronic control system shown in FIG. 5. The three catheter portions12, 16 and 18 are combined to form one integral part, but the portionsmay have different durometers or stiffnesses. The two catheter portions16 and 18 extend parallel to each other and are fused along a majorportion of the catheter 10 and define the two passages 14 and 17,respectively. The distal end of the medication catheter 18 is open, andthe end portion 19 extends through and past the inflatable catheter tipportion 12 so that the catheter tip portion 12 surrounds the medicationcatheter end portion 19. The outer or promixal end of the catheter tube16 is attached to an augmentation pump 35, and the outer or proximal endof the catheter tube 18 is attached to a medication injector pump 36.

The augmentation pump 35 is designed to deliver and withdraw liquidfluid from the tip portion 12 and includes a pump body or housing 38having a tubular tip portion 39 which is coupled to the outer end of thecatheter tube 16. The housing 38 has a bottom flange 42 and receives acylindrical rod or piston 44. A bellows-type rolling diaphragm 46extends over the piston 44 and has an outwardly projecting peripheralflange portion which is clamped and sealed to the housing flange 42 byconcentric sleeve 48. The catheter 10, pump housing 38 and attacheddiaphragm 46 form a sealed disposable unit which is prefilled with apredetermined volume of hydraulic fluid such as the saline solutionmentioned above.

The pump housing flange 42 is secured to a tubular coupling housing 52which has a base flange 53 secured to a pump driver or exciter 55 havinga reciprocating or pulsating piston 56 coupled to the pump piston 44.The pump driver or exciter 55 is adjustable or controllable forselecting the amplitude and frequency of pulsation or reciprocation ofthe piston 56 and the pump piston 44. This control provides forprecisely selecting the frequency of inflation and deflation of thecatheter tip portion 12 by movement of the hydraulic fluid capturedwithin the tip portion 12 and catheter passage 14 and within the pumphousing 38 above the diaphragm 46. The driver 55 has sufficient power toovercome the viscous friction of the liquid within the catheter passage14 and also to overcome the arterial or aortic pressure which opposesinflation of the catheter tip portion 12.

As mentioned above, permanent connections are used to make the catheter10 and pump 35 assembly as an integral self contained unit. Theaugmenting tip 12, augmentation catheter passage 14, and the chamber ofthe augmentation pump housing 38 are prefilled with the pumping liquidand are supplied in sealed sterilized packages. The unit is quicklyattached to the driver or exciter 55 immediately before its use and isdisposed of after treatment.

Different types of drivers or exciters 55 may be used depending upon thespecial requirements of application of the system. One type of pumpdriver is an electromagnetic exciter 55 of sufficient power output,frequency range, and range of displacement amplitude for the piston 56.Another type of driver is an electrical stepping motor which providesfor precise control of the piston 44 of the augmentation pump 35. Theelectromagentic exciter 55 connects with the coupler housing 52 whichconfines linear bearing for guiding the piston 56 to assure accuratereciprocating movement of the piston 56. The outer end of the piston 56is attached by a quick coupling device (not shown) to the augmentationpump piston 44. Either the exciter 55 or coupling housing 52 ispreferably provided with a mechanical stop to limit inflation of thecatheter tip 12 to a maximum safe level.

The operation of the pump 35 and catheter 10 produces a high speedalternating or pulsating action of the tip portion 12 at a frequencysubstantially above the normal pulse frequency of the heart. Forexample, as shown in FIG. 4, the tip portion 12 is pulsed at a frequencyof about 20 Hz. so that nine or ten pulses are produced during thediastolic and part of the systolic or contraction period of each heartpulse. The dynamic characteristics of all parts involved, such as thetip portion 12, the catheter tube 16, the augmentation pump 35 and thedriver 55 are selected to assure a high speed operation over asufficient range of frequencies. This requirement determines the type ofmaterial and wall thickness used for the tube portion 16 and tip portion12. The elastic and inertial properties of the pump 35 and driver 55 areadapted by selecting the moving parts with the correct mass and byadding elastic elements.

The injection pump 36 delivers medication through the medicationcatheter tube 18. The delivery is controlled as to the amount injectedand as to the time of injection. For example, the injection may be madeat one time or in any number of installments at any intervals of timeand in any synchronization with respect to the cardiac cycle of thepatient or in relation to the inflation and deflation of the tip portion12. The medication injection system illustrated, includes a conventionalsyringe 62 which is coupled to the catheter tube 18 and has a plunger orpiston 63 attached to an actuating plate 64. The plate 64 is supportedfor linear movement by a plurality of guide rods 67 which extend betweena set of end plates 68 and 71. The actuating plate 64 also has athreaded hole which receives a lead screw 73 driven by a reversibleelectrical stepping motor 74 mounted on the end support plate 71.

Thus rotation of the lead screw 73 by actuation of the stepping motor 74controls the displacement of the piston 63 of the syringe 62 and therebycontrols the injection of the medication from the syringe 62 through thecatheter tube 18 and its tip or end portion 19. Small incrementalrotation of the lead screw 73 provides for accurate injection of a verysmall volume of medication in timed relation with the actuation of theaugmentation pump 35. A three way valve (not shown) could be installedin the catheter tube 18 in order that the passage 17 may also be usedfor sensing and monitoring aortic blood pressure.

Referring to FIG. 5, an electronic control system controls theaugmentation pump driver or electromagnetic exciter 55 for selecting thevolume of liquid displaced into the inflatable tip portion 12 and thefrequency of inflation. The system also activates the augmenting tipinflation in relation to events occurring during the cardiac cycle byreceiving an input signal from an electrocardiogram (ECG) 80 which ismonitoring the patient's heart pulse. The R-wave from an R-wave detector82 is used as a signal which triggers the activation of the exciter 55after a variable delay period selected by adjusting a variable delayunit 84. The operator sets the delay period, the frequency and amplitudeof pump action, the duration of pump action, and the inflation rate-timerelation (for instance sinusoidal, triangular, rectangular, ramp, singlestep, succession of steps, etc.).

The operation of the augmentation pump exciter 55 is controlled by afunction generator 86. The function generator is set to produce analternating output signal of a selected frequency, amplitude and waveshape, and the output signal forms an input to a power amplifier 88which feeds an amplified signal to the exciter 55.

Since the electromagnetic exciter 55 is not a "stiff" driver, a feedback loop 89 is used when a particular piston position must be heldmomentarily. The feed back loop 89 consists of a position transducer 92attached to the piston 56 of the driver 55. The transducer 92 generatesa signal in proportion to the piston displacement, and this signal isfed into a summing amplifier 94.

The summing amplifier 94 is inserted between the function generator 86and the power amplifier 88 and determines the difference between thesignal coming from the function generator 86 and the signal coming fromthe displacement transducer 92 and feeds this difference into the poweramplifier 88. The output of the summing amplifier 94 and consequentlythe input to the power amplifier 88 is zero if the piston 56 is in theposition as demanded by the function generator 86. Any discrepancyresults in a signal from the summing amplifier 94 to the power amplifier88 which, in turn, corrects the position of the piston 56.

The above description applies to the basic electronic instrumentationthat is required to control the electromagnetic exciter 55 on acontinuous basis if no triggering through an external signal isrequired. In some applications the driver or exciter 55 must be startedand stopped in timed relation with the cardiac cycle. For example, theaugmenting tip 12 must be evacuated and stopped at the end of theisometric contraction period, as shown in FIG. 4.

The R-wave from the electrocardiogram 80 is used as the point ofreference for starting and stopping the exciter 55. Thus the patient'sECG is monitored and recorded on a multi-channel triggered oscilloscope100 (FIG. 5) for observation. The ECG signal is also an input into aR-wave detector 82 which detects either the slope at the onset of theR-wave or the instance at which the R-wave exceeds a certain voltagelevel. The R-wave detector 82 then transmits a pulse to the variabledelay unit 84.

If the pulse from the R-wave detector 82 was transmitted directly to thefunction generator 86, this would immediately trigger the functiongenerator 86 and inflate the augmenting tip portion 12 during thesystolic period. The tip portion 12 cannot be inflated during thisperiod because of the related intolerable increase of ventricularpressure. The activation of the function generator 86 is thereforedelayed in relation to the R-wave. The pulse from the R-wave detector 82is transmitted to a circuit which delays the transmission to thefunction generator. The period of delay is adjustable and triggers theoperation of the pump system in relation to the R-wave.

The ECG and aortic blood pressure are displayed on a multichanneltriggered oscilloscope 100 so that the user may observe the effect ofthe augmenting pump operation on the aortic pressure pulses and theirplacement and duration within the cardiac cycle. This informationenables the user to correct or adjust the placement of the series ofpressure pulses within a cardiac cycle by adjusting the delay time. Thedisplay of the ECG and aortic pressure on the scope 100 is triggered byusing the impulse from the R-wave detector 82. An almost standingpicture of ECG and aortic pressure may be produced on the display screenof the oscilloscope 100, thereby greatly aiding the interpretation ofboth recordings.

The actuation of the tip portion 12 as to wave shape, frequency,amplitude, and period of operation in relation to cardiac events isselected according to each medical case. The aortic pressure, the ECGR-wave, the display of these signals on the trigger oscilloscope 100,the variable delay 84 and the function generator 86 may also be used forcontrolling a stepping motor and lead screwdriver 106 (FIG. 6) which maybe used in place of the electromagnetic exciter 55. A stepping motor isan inherently stiff driver, and current is maintained on the motorwindings when the motor is not being stepped for producing a highholding torque. The feed back loop consisting of the position transducer92 and summing amplifier 94 is not essential for a stepping motor, butmay be retained to serve as a precision control and safety control forthe stepping motor. The power amplifier shown in FIG. 5 is replaced by atranslator module 105 (FIG. 6) to control the operation of the steppingmotor 106 which replaces the electromagnetic exciter 55.

As also shown in FIG. 6, the medication pump 36 is actuated by anelectronic control which permits injection of medication in various wayssuch as in one-shot or in successive steps. This requires a control overthe frequency of injection and the advance of the piston 63 in timedrelation to either a cardiac event or to the inflation and deflation ofthe augmenting tip portion 12. The additional controls shown in FIG. 6are the same controls as required for the control of the augmenting tipportion 12 and includes a variable delay 114, a function generator 116and a translator module 125 for controlling the operation of thestepping motor 74 of the medication pump. The position of the injectionpump 36 is sensed by a transducer 128 and displayed on the scope 100 sothat the user may adjust the injection time in relation to aorticpressure or to other cardiac events by using the variable delay 114.

It is thus apparent from the above description that the method andapparatus of the invention may be used for treating pre-infarctionangina, a pathophysiological state of regional tissue ischemia anddecrease in normal muscle function. This state is usually caused byblockage of a coronary artery by an atherosclerotic intra-luminal mass.The augmentation in accordance with the invention may be used to open upcollateral vessels immediately after the coronary arteriography whichidentifies the cause. The catheter pulsating close to the coronary ostiato deliver short burst of energy is effective to open up the collateralvessels. In a coronary care unit, the pulsation may be monitored byexisting equipment and its effectiveness measured by the return tonormal function of the heart muscle and the improvement of thepre-infarcation angina.

The invention may also be used in connection with bypass open heartsurgery when there exists a pathophysiological state of global hearthypoxia related to a low total body blood pressure and flow. Thecoronary blood flow may be completely stopped for periods of 5 to 10minutes then reperfusion accomplished by unclamping of the thoracicaorta. This cycle may be repeated several times for a total bypass timeof two hours, more or less. Return of normal cardiac muscle function maybe delayed for one to three days, and regional ischemia/myocardialinfarction occurs in 10 to 20% of the cases. The augmentation system maybe used prior to bypass surgery and during each period of unclamping theaorta for reperfusion and for the one to three days following surgery.With the inflatable tip portion 12 close to the coronary arteries, thegeneration of pressure levels greater than the critical openingpressures of the numerous small coronary arteries would increase totalblood flow to the cardiac tissues. The reversal of progressive hypoxiaduring bypass surgery and more rapid return toward normal function maybe evaluated both at the surgical table and in the post-surgicalintensive care unit. This technique should lessen the morbidity andmortality of open heart surgery.

The method and apparatus of the invention may also be used for a shockeda kidney which is a pathophysiological state in which a temporarydecrease in systemic blood pressure is associated with a prolonged lossof normal kidney function. In spite of return to normal systemic bloodpressure, regional blood flow to the kidney remains low. The decreasedkidney function may not be detected for hours after the insult.Management presently consists of control of blood volume, electrolytebalance and stimulation of kidney function by tubular diuretics andosmolar solutions. During the prolonged ten to twenty days of kidneymalfunction, renal dialysis may be necessary to sustain life. During andafter an episode of hypotension, the augmenting tip portion 12 may besituated close to the renal artery take off from the abdominal aorta inorder to reopen the small renal arteriols by the dynamic pressure waveform. The reestablishment of the renal vascular pressure gradient andtubular perfusion by the technique would prevent the shock kidney stateand resultant morbidity.

Another use of the augmentation pump device of the invention is inconnection with organ transplant when there normally occurs apathophysiological state of whole organ anoxia resulting from abruptloss of blood flow and pressure during removal of the organ (kidney,heart, liver, etc.) from the donor's body. Implantation of the organinto the recipient's body and restoration of the blood flow by surgicalanastomosis of the arteries and veins do not result in immediate returnof tissue viability in the transplanted organ. The augmentation pump ofthe invention may be used in the donor's body prior to removal of theorgan to maintain blood pressure above the critical closing pressure andin the receptor's body following the vessel anastomosis to exceed thecritical opening pressure of the transplanted organ. Viability oftissues should be enhanced by this procedure during the critical periodof removal and also to improve the organ function in the recipient'sbody.

While the method and form of pump apparatus herein described constitutea preferred embodiment of the invention, it is to be understood that theinvention is not limited to the precise method and form of apparatusdescribed, and that changes may be made therein without departing fromthe scope and spirit of the invention as defined in the appended claims.

The invention having thus been described, the following is claimed:
 1. Amethod for perfusing a body organ or tissue containing a body fluid,comprising the steps of forming a catheter having an inflatable portionand enclosing a fluid adapted to be pulsated, inserting the inflatableportion of the fluid-filled catheter into a vessel within the organ ortissue, and pulsating the fluid enclosed within the catheter at afrequency substantially greater than the normal pulsation frequency ofthe heart for transmitting pulsatile energy and for producing anamplified dynamic pressure wave form in the body fluid in response toinflation and deflation of the inflatable catheter portion to increasethe penetration of the body fluid into the microcirculatory resistancevessels within the body tissue or organ.
 2. A method as defined in claim1 and including the steps of monitoring the pulsation of the heart, andproducing repetitive trains of pulses in timed relation with thepulsation of the heart.
 3. A method as defined in claim 2 wherein therepetitive trains of pulses are produced during the diastolic periodand/or isometric contraction period of the heart.
 4. A method as definedin claim 1 and including the step of selecting the amplitude andfrequency of pulsation in accordance with a specific physiologicalrequirement.
 5. A method as defined in claim 1 and including the step ofrepetitively inflating and deflating the inflatable catheter portion intimed relation with heart pulses for generating and transmittingamplified pressure waves into tissue areas or organs during selectedportions of the cardiac cycle.
 6. A method as defined in claim 1 andincluding the step of producing pressure waves with sufficient amplitudeto open previously collapsed small vessels within the tissue or organ.7. A method as defined in claim 1 including the steps of monitoring theaortic blood pressure and the heart pulse of a patient, producing avisual display of the blood pressure and heart pulse, and pulsating theblood at the substantially greater frequency and in timed relation withthe pulsation of the heart.
 8. A method as defined in claim 1 andincluding the step of injecting a predetermined volume of medication intimed relation with the pulsating of the liquid.
 9. Apparatus forperfusing a body organ or tissue containing a body fluid, comprising acatheter having an inflatable portion and enclosing a fluid adapted tobe pulsated, the inflatable portion of the fluid-filled catheter adaptedto be inserted into a vessel within the organ or tissue, and means forpulsating the fluid within the catheter at a frequency substantiallygreater than the normal pulsation frequency of the heart fortransmitting pulsatile energy and for producing an amplified dynamicpressure wave form in the body fluid in response to inflation anddeflation of the inflatable catheter portion to increase the penetrationof the body fluid into the microcirculatory resistance vessels withinthe body tissue or organ.
 10. Apparatus as defined in claim 9 andincluding control means for operating said pulsating means in timedrelation with the heart pulsation.
 11. Apparatus as defined in claim 9wherein said inflatable portion of the catheter defines an annularchamber surrounding a tubular catheter portion defining a passage. 12.Apparatus as defined in claim 9 including means for injecting amedication fluid through the catheter.
 13. Apparatus as defined in claim9 including means for sensing the pulsating of the heart, and time delaymeans for actuating said pulsating means in response to operation ofsaid sensing means.